Don't drag scrollbars if they're not visible

src/backend/curses/n.rs

@@ -89,18 +89,19 @@ impl InputParser {
         if ncurses::getmouse(&mut mevent as *mut ncurses::MEVENT)
             == ncurses::OK
         {
-            // eprintln!("{:032b}", mevent.bstate);
             // Currently unused
+            let _ctrl = (mevent.bstate & ncurses::BUTTON_CTRL as mmask_t) != 0;
             let _shift =
                 (mevent.bstate & ncurses::BUTTON_SHIFT as mmask_t) != 0;
             let _alt = (mevent.bstate & ncurses::BUTTON_ALT as mmask_t) != 0;
-            let _ctrl = (mevent.bstate & ncurses::BUTTON_CTRL as mmask_t) != 0;
 
+            // Keep the base state, without the modifiers
             mevent.bstate &= !(ncurses::BUTTON_SHIFT
                 | ncurses::BUTTON_ALT
                 | ncurses::BUTTON_CTRL)
                 as mmask_t;
 
+            // This makes a full `Event` from a `MouseEvent`.
             let make_event = |event| Event::Mouse {
                 offset: Vec2::zero(),
                 position: Vec2::new(mevent.x as usize, mevent.y as usize),

src/views/scroll_view.rs

@@ -189,7 +189,11 @@ where
 
     /// Returns the size available for the child view.
     fn available_size(&self) -> Vec2 {
+        if self.show_scrollbars {
             self.last_size.saturating_sub(self.scrollbar_size())
+        } else {
+            self.last_size
+        }
     }
 
     /// Compute the size we would need.
@@ -231,20 +235,21 @@ where
     ///
     /// Returns `true` if the event was consumed.
     fn start_drag(&mut self, position: Vec2) -> bool {
+        // For each scrollbar, how far it is.
         let scrollbar_pos = self.last_size.saturating_sub((1, 1));
 
-        let grabbed = scrollbar_pos.zip_map(position, |s, p| s == p);
+        // This is true for Y if we grabbed the vertical scrollbar
+        let grabbed = scrollbar_pos.zip_map(position, |s, p| s == p).swap();
 
         let lengths = self.scrollbar_thumb_lengths();
         let offsets = self.scrollbar_thumb_offsets(lengths);
 
-        // See if we grabbed one of the scrollbars
+        // Iterate on axises, and keep the one we grabbed.
         for (orientation, pos, length, offset) in
             XY::zip4(Orientation::pair(), position, lengths, offsets)
-                .zip(grabbed.swap())
+                .keep(grabbed.and(self.enabled))
                 .into_iter()
-                .filter(|&(_, grab)| grab)
-                .map(|(x, _)| x)
+                .filter_map(|x| x)
         {
             if pos >= offset && pos < offset + length {
                 // We grabbed the thumb! Now scroll from that position.
@@ -262,7 +267,9 @@ where
         false
     }
 
+    /// Called when a mouse drag is detected.
     fn drag(&mut self, position: Vec2) {
+        // Only do something if we grabbed something before.
         if let Some((orientation, grab)) = self.thumb_grab {
             self.scroll_to_thumb(
                 orientation,
@@ -466,7 +473,8 @@ where
                         event: MouseEvent::Press(MouseButton::Left),
                         position,
                         offset,
-                    } if position
+                    } if self.show_scrollbars
+                        && position
                             .checked_sub(offset)
                             .map(|position| self.start_drag(position))
                             .unwrap_or(false) =>
@@ -477,7 +485,8 @@ where
                         event: MouseEvent::Hold(MouseButton::Left),
                         position,
                         offset,
-                    } => {
+                    } if self.show_scrollbars =>
+                    {
                         let position = position.saturating_sub(offset);
                         self.drag(position);
                     }

src/xy.rs

@@ -140,6 +140,11 @@ impl<T> XY<T> {
     {
         XY::new(f(self.x, other.x), f(self.y, other.y))
     }
+
+    /// For each axis, keep the element from `self` if `keep` is `true`.
+    pub fn keep(self, keep: XY<bool>) -> XY<Option<T>> {
+        keep.select(self)
+    }
 }
 
 impl<T: Clone> XY<T> {
@@ -192,6 +197,16 @@ impl XY<bool> {
     pub fn select_or<T>(&self, if_true: XY<T>, if_false: XY<T>) -> XY<T> {
         self.select(if_true).unwrap_or(if_false)
     }
+
+    /// Returns a term-by-term AND operation.
+    pub fn and(&self, other: Self) -> Self {
+        self.zip_map(other, |s, o| s && o)
+    }
+
+    /// Returns a term-by-term OR operation.
+    pub fn or(&self, other: Self) -> Self {
+        self.zip_map(other, |s, o| s || o)
+    }
 }
 
 impl<T: Copy> XY<T> {